DETERMINATION OF PHOSPHORUS in ASPHALT BINDERS & in BINDERS RECOVERED from BITUMINOUS MIXTURES. By GERALD REINKE STACY GLIDDEN

Transcription

1 DETERMINATION OF PHOSPHORUS in ASPHALT BINDERS & in BINDERS RECOVERED from BITUMINOUS MIXTURES By GERALD REINKE STACY GLIDDEN

2 STEP ONE DEVELOPMENT OF EDXRF ANALYSIS PROCEDURE of ASPHALT to DETERMINE PHOSPHORUS CONTENT

3 Purpose To develop a quick and accurate test method by which percent phosphorus in asphalt could be determined. This could then be used to determine the amount of polyphosphoric acid that was added to an asphalt sample.

4 Assumptions Virgin asphalt does not contain phosphorus Sample tested by DataChem with an ICP was BDL Percent phosphorus can be converted back to polyphosphoric acid if the type of acid used is known ex. 115%, 105%, etc. Deconvolution software is able to differentiate between S and P peaks

5 Instrument EDXRF Epsilon 5 manufactured by Panalytical with a 600 W Gd-anode X-ray tube and 100kV generator.

6 Standards 27 Standards 4 Base Asphalts 115% Polyphosphoric Acid, Reagent Grade S Range: 1.8% to 4.5% P Range: 0.00% to 0.54% Conversion to 115% Polyphosphoric Acid: 0.0% to 1.5% Acid in Asphalt

7 Standard ID % P % S Standard ID % P % S

8 Sample Preparation Empty Sample Holder Filled Sample Holder Sample in Liquid XRF Cup Bottom View of Sample in Liquid XRF Cup

9 Thanks to Olga Puzic for identifying that direct pour can work with Mylar film, although at high enough temperature it will definitely melt

10 Application Meas. Secondary Element Time (sec) Target Line P 600 CaF 2 Ka S 600 CaF 2 Ka

11 Deconvolution S: Ka = 2.3 P: Ka = 2.0

12 P Calibration RMS = Correl. =

13 Repeatability Plant production sample with a calculated formulation target of 0.109% P 4.7% higher than target Run # % P Average Std Dev

14 ADDITIONAL CONFIRMATORY TEST RESULTS Eight samples submitted by Port Authority of New York & New Jersey Samples submitted blind Technician at Port Authority lab added differing amounts of 105% PPA to samples they received from suppliers. Two suppliers represented Data used with permission from PANYNJ

15 SAM PLE PG GRADE used to make blend Wt% P determin ed Wt% of 105% PPA reported Wt% Sulfur Wt% of 105% PPA reported added by PANYNJ A No PPA B C SBS D SBS E SBS No PPA F SBS G No PPA H Comments from PANYNJ PPA had partially solidified and some adhered to spatula, somewhat lower result expected. Sample D contained 0.35% PPA according to supplier 0.35%+0.645%=0.995%

16 STEP TWO DEVELOPMENT OF PROCEDURES FOR EXTRACTION, RECOVERY AND DETERMINATION OF PHOSPHORUS IN MIXTURES

17 FOLLOW-UP TESTING Sample prepared at a calculated 0.746% of 115% PPA (0.746*0.3631= 0.271% P EDXRF result 0.269% P or 0.741% PPA MIX TESTING TO BE PERFORMED Use granite, siliceous gravel, limestone aggregates. Mix 6% binder with material finer than 4.76 mm sieve, condition overnight at 100 C Extract, recover the binder. Test for %P in binder Crush recovered aggregate, test for %P and compare to virgin aggregate result

18 % Phosphorus in Binder Recovered from mix using ambient temperature extraction 0.269% P in original binder Cisler/granite Wimmie/siliceous gravel Waldenberger/limest one % Phosphorus in binder as determined by EDXRF 0.269% 0.269% 0.269% n-propyl Bromide # % 0.211% 0.149% n-propyl Bromide # % 0.160% 0.177% 85% Toluene & 15% Ethanol 0.029% 0.151% 0.017%

19 % Phosphorus Recovered by Extraction Cisler/granite Wimmie/siliceous gravel Waldenberger/lime stone % Phosphorus in binder as determined by EDXRF 0.269% 0.269% 0.269% n-propyl Bromide #1 n-propyl Bromide #1 38.3% 78.4% 55.4% 27.1% 59.5% 65.8% 85% Toluene & 15% Ethanol 10.8% 56.1% 6.3%

20 ADDITIONAL EXTRACTION TESTS Binder used to make mixes contained 0.269% 1.32 kpa 64 C % P in recovered binder after 1 extraction % P in recovered binder after 2 extractions THF Extracted granite agg THF extracted limestone agg 0.088% P equals 32.7% recovery 0.102% P equals 37.9% recovery 0.122% P Equals 45.3% recovery C C Appears as though THF is no more effective as a primary extraction solvent than n- Propyl Bromide

21 WATER SOAK OF RECOVERED AGGREGATE Soaked granite agg from toluene ethanol extraction in distilled 60 C % P in water = 0.029% in 100 ml % P in water from virgin granite soaked in water = 0.024% in 100 ml Soaked limestone aggregate from THF extraction in distilled 60 C % P in water = 0.019% in 150 ml % P reading in distilled water = 0.014% Would appear that soaking has little if any effect on removing P from aggregate

22 ATTEMPS AT MORE QUANTITATIVE DETERMINATION Determined %P in each aggregate prior to mixing with binder Granite 1.67% Gravel 1.096% Limestone 0.344% Determined %P in each aggregate after extraction, a total of 300 g aggregate was mixed with 19 g AC treated with 0.75% PPA by wt which provides 19*.0075*.3674= g P Granite 1.78% ( )*300=0.33 g P Gravel 1.031% which yields negative P Limestone 0.725% = g P

23 SECONDARY EXTRACTION OF RECOVERED AGGREGATE PROCEDURE FOLLOWED Recovered aggregate was further extracted with THF filtered and centrifuged to remove fines THF evaporated with heat lamp Residue solubilized in n-propyl Bromide (npb) and added to virgin asphalt sample Flashing npb from molten asphalt presents some spattering issues, however less dangerous than flashing THF into molten asphalt

24 n-propyl Bromide extraction #2 of granite aggregate yielded 0.073% P or g of P in 19 grams of binder used in the mix THF used to perform a secondary extraction. THF evaporated, residue solubilized in n-propyl bromide and flashed into 24.8 g of binder % P in this binder was 0.138% or g of P Total wt of Phosphorus = g or a total recovery of 92% (.048/0.0518)

25 SUMMARY & FURTHER WORK Secondary or tertiary extraction of extracted aggregate can lead to greater recovery of phosphorus from mixes produced with PPA modified binders This work needs more follow-up testing Future extraction work using Soxhlet extractor of mixes with refluxing solvent to determine if this method can lead to greater phosphorus recovery

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27 THREE CORES RECEIVED FROM PORT AUTHORITY OF NEW YORK & NEW JERSEY TO BE TESTED FOR PHOSPHORUS CONTENT MIX EXTRACTED WITH n-propylbromide IN SOXHLET EXTRACTOR AND RECOVERED WITH ROTOARY EVAPORATOR APPEARS AS THOUGH THE Sample %P SOLVENT IS REMOVING Theoretical %PPA (115%) Core PHOSPHORUS FROM THE Core AGGREGATE Core Virgin aggregate 1.458% NA

28 For germanium the escape peak is 9.87 kev left of the parent peak. Bromine is kev which means the the escape peak is at =2.037 Phosphorus is kev. Escape peak is 1% of the parent peak, which is l begin with.

29 AGGREGATE RECEIVED FROM PORT AUTHORITY WAS MIXED WITH CONTROL BINDERS AND EXTRACTED WITH TRICHLOROETHYLENE AND RECOVERED FOR PHOSPHORUS DETERMINATION APPEARS AS THOUGH Sample %P %P present in binder TRICHLORETHYLENE ALSO IS REMOVING PHOSPHORUS FROM THE AGGREGATE

30 FINALLY WE SWITCHED TO TETRAHYDROFURAN (THF) Sample %P Theoretical or actual %P present in binder Percent phosphoru s recovery Core Core Core acid modified %

31 NY-NJ Port Authority, Core #13, Rec AC, MSCRB, 70, 3200 Pa Stress PG % strain time global (s)

32 NY-NJ Port Authority, Core #11, Rec AC, MSCRB, 70, 3200 Pa Stress PG PANYNJ CORE 11 RECOVERED AC MSCR, 70 C, 3200 Pa % strain PG PANYNJ CORE 7 RECOVERED AC MSCR, 70 C, 3200 Pa time global (s)

33 PROCEDURE FOR DETERMINING PHOSPHORUS IN BITUMINOUS MIXES 1. Sample of job aggregate needed Determine phosphorus content of aggregate 2. Mix job aggregate with 2 control binders one with 0% P and one with a know level of P Extract and recovery with Soxhlet using n-propylbromide. This would be preferable to THF If it appears that npb is removing P from aggregate, switch to THF

34 PROCEDURE CONTINUED 3. From what we have seen most aggregates do not release their phosphorus to the solvent. Running the control binders will give a good indication of how intensively the aggregate holds on P from PPA or how readily the aggregate gives up its P 4. Run the extraction and recovery of the mix in question

35 PROCEDURE CONTINUED 5. Soxhlet procedure Use grams of mix (should yield 6+ grams of binder. Sufficient to run XRF test Extract in Soxhlet for 3 hrs We have found that we need to control the extraction time to achieve consistent results between controls and unknowns 6. Recovery procedure for THF using Rotovap Recovery Temp=125 C, Argon gas purge 500 ml/min Start argon purge at 750 mbar (560 mm Hg) ramp down to 200 mbar (150 mm Hg) below 200 mbar THF boils in receiving flask Starting rpm=25 ramp to 45 rpm in the 30 minutes at 200 mbar 30 minutes at 200 mbar to be sure all THF removed since the vacuum isn t as low as when we use npb

36 SUMMARY & FURTHER WORK EDXRF is a suitable and accurate test method for determining percent P typically found in PPA modified asphalt blends. Deconvolution of P and S is possible at levels which are typically found in asphalt. P in asphalt can be analyzed much faster than with the typical ICP method although with less precision at very low concentrations.

37 SUMMARY & FURTHER WORK Typical extraction solvents (n-propyl Bromide, Toluene/Ethanol, Tetrahydrofuran) remove differing amounts of phosphorus as a function of the solvent Granite, siliceous gravel, and limestone appear to hold on to phosphorus at differing levels after extraction of asphalt recovery not quantitative Some aggregates will release P into extraction solvent

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